not gaining weight 🙄

So I'm 17 weeks and 3 days, little princess due November the 10th... When I found out I was pregnant I weighed in at 9 stone 6 I weighed myself yesterday and I am only 9 stone and 10 that means I have only gained 4lb in 14 weeks, my midwife has estimated I gain 23-35lb through the whole pregnancy I am now worrying that I ain't gaining enough weight anyone else not put on hardly any weight and haven't got much of a bump to put my mind at rest??